Autopsy samples from cerebral areas of 5 brains from patients with multiple sclerosis (MS) and from 6 control brains were stained with Perls'' aid ferrocyanide to detect nonheme Fe present as hemosiderin. Positive Fe reactions were observed only in MS sections surrounding demyelinated plaques. Myelinated white matter near the lesion contained numerous Fe-laden ovoid bodies and axons that stained positively for Fe. Positive reactions were also found within blood vessels of gray matter near the lesion. A possible source of the Fe was extravasated blood.